1. Field of the Invention
The present invention relates to an ink jet recording apparatus, and particularly, to an ink jet recording apparatus used as an information recording apparatus for an electronic typewriter, a word processor, a facsimile, a copying machine and so on.
2. Description of the Related Art
There have been proposed recording apparatuses which use various types of recording heads depending on respective recording methods, and record information on a recording medium such as paper, OHP sheet and so on; the recording medium is hereinafter called simply a recording paper or a paper. These recording methods include wire-dot recording method, thermal-sensitive paper recording method, thermal transcription recording method and ink jet recording method and so on.
Among these methods, the ink jet recording method, in which ink droplets are ejected to the recording paper, has attracted a great deal of attention with its advantageous aspects such as low cost in fabricating and operating the apparatus and low noise in recording.
In addition, in recent ink jet recording apparatus, especially with respect to the recording head used in the ink jet recording apparatus, the fabrication process of the recording head is much supported by the semiconductor device technologies such as thin film growth technology and microscopic device process technology, and recording heads fabricated in much smaller dimension and with lower costs are realized. In response to this technical progress in fabricating recording heads, the structure and dimension of the recording apparatus are getting smaller and simplified.
The ink jet recording apparatus having the above described advantageous features is used as a recording apparatus in electronic typewriters, word processors, facsimiles and copy machines and so on. In every application, the ink jet recording apparatus is formed so as to be suited to the required functions and the usage specific to the application apparatus.
There has been a recent trend in electronic typewriters and word processors towards being fabricated small-sized, lightweight and portable. This trend also requires the compact and much simplified ink jet recording apparatus.
Under the above described trend, that is, the trend of compact and simplified structure of the ink jet recording apparatus, it is required to simplify units forming an ink jet recording apparatus and furthermore to simplify mechanisms connecting these units to each other.
Among these units and mechanisms, the above requirements are applicable to an intermediate tank installed on the ink supply route between a ink tank and the recording head and used for cushioning the pressure deviation in the ink supply route in order to establish stable supply of ink to the recording head. Especially, in the case that a plurality of different colored inks and a corresponding plurality of recording heads are used, there is a problem that the structure of the intermediate ink tank and ink tubes becomes complex and the size thereof becomes large.
An ejection recovery unit of the ink jet recording apparatus has a cap, a pump for sucking ink through the cap and a unit for driving the pump and the cap. Simplification of the ejection recovery unit also leads to the effective reduction in size of the ink jet recording apparatus.
Additionally, in the above described trend, an increase in viscosity of ink and solidification of ink bring a relatively large adverse effect on the ink jet recording apparatus. For example, as the size of an ink ejection outlet of the recording head and an ink passage connecting to the ink ejection outlet are very small, the viscosity of the ink has a relatively large effect on the ink ejection ability of the recording head.